Various technical solutions are known in the field of monitoring persons with respect to the use of illicit substances, especially alcohol or other drugs. The testing of a breath sample is performed with prior-art systems optionally either at different sites by means of a mobile breath alcohol measuring device, for example, for monitoring vehicle drivers, or at fixed locations, especially for monitoring persons subject to house arrest rules.
Mobile devices are often used by the police or other regulatory agencies, which exercise official duties, in order to test especially vehicle drivers for the use of illicit substances. Stationary devices are installed, by contrast, above all in the household of a person who has been sentenced to house arrest in order to monitor compliance there with the house arrest rules, especially with respect to the ban on the use of illicit substances.
It may thus be necessary for various reasons to compare the identity of a person giving a sample with the person to be monitored. This is especially true in case of persons who have become noticed on several occasions because of alcohol-related offenses and must therefore use a monitoring system for monitoring the alcohol level at home.
At the beginning of such a measure, the person to be monitored must give a biometric sample as a basis for verification. This is preferably a fingerprint or a photo. In the further course of the measure, the person to be monitored must give a sample at fixed intervals in order to have, for example, the alcohol level in the breath checked. The agreement of the identity of the person giving the sample with the person to be monitored based on the biometric sample should be checked without the person giving the sample having to be excessively cooperative. It is essential for this that the handling of the corresponding monitoring systems is simple and does not call for any special requirements adapted to the conditions prevailing in the area surrounding the monitoring system, especially on light and noise conditions. A special biometric characteristic of the person to be monitored is recorded in the prior-art systems that check the identity of a person who must give a breath sample, usually before the beginning of the test proper, and compared with a biometric reference characteristic stored in the system. Fingerprints or photos of the person to be monitored are usually recorded/taken and analyzed as a basis of verification in prior-art systems.
A house arrest system, which is a detention and person monitoring system for prisoners or for persons conditionally released from custody on probation, who are subject to house arrest, house detention or a so-called unsupervised custody, is known in this connection from DE 38 83 763 T2. It is possible by means of the system described to monitor the presence of the prisoner at an unsupervised location and at the same time to monitor compliance with certain custody rules. A stationary device, which is optionally equipped with different means for detecting and monitoring biometric characteristics of the person to be monitored, is provided for this. In addition to the determination of the breath alcohol content of the person to be monitored, it is possible with the technical solution described to detect at least one biometric characteristic, e.g., a visible image information, a voice print or a fingerprint, in order to compare this detected characteristic with a known characteristic stored in the system. In case of violation of the custody rules or of the rules for properly performing the test, an external agency is informed of this by means of a suitable electronic message.